This invention is directed to microelectromechanical systems (MEMS) which are used as electrical switches. In particular, this invention is directed to a MEMS structure which has a higher resistance, sacrificial switch as well as a lower resistance switch.
Microelectromechanical systems (MEMS) are devices which may be fabricated using semiconductor thin film technology in order to reduce the characteristic dimensions of the devices. MEMS technology is often applied to the design and fabrication of actuators, particularly those with a limited range of motion. MEMS technology has been applied to the design and fabrication of electrical switches, for example, to open and close contacts which form an electrical circuit. MEMS techniques may be used to batch fabricate small switches in large quantities relatively inexpensively, as lithographic processing techniques are employed.
One example of a prior art MEMS switch is shown in FIG. 1. MEMS switch 1 includes a cantilevered beam 4 carrying a shunt bar 6, which is lowered down onto a pair of contacts 5, to provide an electrical connection between the contacts 5, and thereby close the switch 1. The force for lowering or raising the cantilevered beam 4 is provided by, for example, a pair of electrostatic plates (not shown), if the switch is an electrostatic switch. However, it should be understood that other mechanisms may also be used to provide the force to close the switch, for example, electromagnetic forces.
A figure of merit for electrical switches is the residual resistance when the switch is in the “on” state. This residual resistance may determine the heat dissipated by the switch as well as the maximum frequencies which can be handled by the switch without unacceptable attenuation of the signal. In order to reduce this residual resistance as much as possible, the contact between the shunt bar 6 conductors and the contacts 5 needs to be as intimate as possible.